The invention uses various materials which are electrically either conductive, insulating or semiconducting, although the completed semiconductor circuit device itself is usually referred to as a "semiconductor". One of the materials used is silicon, which is used as either single crystal silicon or as polycrystalline silicon material, referred to as polysilicon or "poly" in this disclosure.
Shallow channel junction will reduce significantly the undesirable short channel effects of transistors. This is significant in the fabrication of sub-micron P-channel (P-CH) transistors in which n+ doped poly gate is used and buried channel is formed. It is desired to further reduce or even solve P-channel buried channel-induced short channel effects and enable further decrease in device length to the sub-micron range.
The prior art relating to Germanium in VLSI devices has been in the area of (1) field isolation improvement and (2) transistor source/drain regions to achieve shallow source and drain junctions. The former deals with device isolation and an improvement in electrical encroachment; yet it does not improve transistor performance; the later deals with device performance by means of achieving shallower source drain junction depths so that the reduction in charge-sharing effect would improve transistor short channel characteristics. It however does not solve or reduce P-channel transistor short channel effects caused by the very nature of buried channel behaviour.